Three dimensional projection arrangement

ABSTRACT

A projection arrangement for projecting three-dimensional images of objects into space. The object is illuminated by a source of light, and the light rays reflected from the object are directed so as to be incident on a mirror surface located behind a lens. The mirror surface receives an image from the lens and the combination forms an enlarged three-dimensional image projected into space. The lens can be in the form of a modified Fresnel lens of multiple focal lengths and having spherical zones in the form of strips. The Fresnel lens, which may be used in combination with other optical elements, provides a substantially large field of view suitable for viewing a three-dimensional image of the object by a mass audience. The image projection may be achieved without the use of a screen. The enlarged three-dimensional image appears floating in space visible to unaided eyes of an audience.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of application Ser. No. 082,211, filedOct. 4, 1979, now abandoned which is a continuation-in-part ofapplication Ser. No. 917,400, filed June 20, 1978, now abandoned.

BACKGROUND OF THE INVENTION

This invention pertains to an image projection arrangement forprojecting enlarged three-dimensional images of objects into space forviewing by observers.

Image projection from transparencies onto flat or curved surfaces oronto screens is well known. For example, U.S. Pat. No. 3,293,982 toAppeldorn and U.S. Pat. No. 3,340,765 to Herriott disclose systems foroverhead projection of images from a transparency onto a displacedscreen, whereby light is transmitted through the transparency, thenreflected back and projected onto the screen. However, these devicesproject only flat two-dimensional images. U.S. Pat. No. 1,866,870 toO'Neill discloses an apparatus which projects a three-dimensional form,but it provides only minor magnification or enlargement of the image andhas a limited viewing zone. Also, U.S. Pat. No. 3,293,983 to Gaudyndiscloses a display device utilizing a parabolic mirror and conventionalFresnel lens to project a three-dimensional image of an object intospace for side viewing.

A spherical lens, when the diameter is large and surpasses the radius ofcurvature, becomes bulky. Since refraction is accomplished at thesurfaces, the major spherical part can be removed and a conventionalFresnel lens is thereby constructed. A conventional Fresnel lens is aflat thin piece of glass or plastic in which are molded a series ofsmall concentric stepped zones extending from center to outer margin.Each groove provides a minute refracting facet capable of bending light.

SUMMARY OF INVENTION

It is an object of the present invention to provide a projectionarrangement for objects in which a three-dimensional image of the objectis formed in space and may be viewed by unaided eyes of numerousobservers.

Another object of the present invention is to provide a projectionarrangement of the foregoing character which uses a modified Fresnellens and is substantially simple in construction and may be economicallyfabricated and operated.

In the present invention, a three-dimensional projection arrangement isprovided which uses a multifocal refracting lens in combination with areflecting mirror surface movable relative to the lens, such as amodified Fresnel lens together with a curved reflecting mirror, locatedbehind the lens to provide a three-dimensional image of an objectprojected into space for viewing by an audience. This reflecting mirroris preferably movable relative to the lens to provide adjustablemagnification of the image.

By a modified Fresnel lens is meant a flat lens of transparent glass orplastic material and containing a plurality of facets for which themultiple focal points are modified by a lens correction element. Themodified Fresnel lens may have multiple focal lengths, having sphericalzones in the form of strips rather than concentric rings as in theconventional type lens. A preferred lens configuration has its curvedsurface in the shape of a cycloid.

In space projection, the sphero-parabolic, fully modified Fresnel lensis a basic form. There are other regular combinations: sphero-elliptic,sphero-hyperbolic, double parabolic, etc. but the principal parts arethat the system has to be concave and the first surface must betransformed into a Fresnel-type lens.

A reflecting system has many advantages over the refracting system inthat chromatic, spherical aberrations, coma, astigmatism, and Petzvalsum are either not existent or are greatly reduced. However, thereflecting system has an inherent drawback, namely, the obstruction ofthe incident light by the solid object or by some essential subsequentoptical component.

The beam of light that forms the image is composed of hollow cones oflight rays which result in a very poor quality of the image. In order toremove this malfunction, use can be made in the present invention of avariation of the split lens arrangement. The halves of the lens arepreferably separated along the lateral and/or longitudinal optical axis,so that the light reflected from the object will use the lower part ofthe lens below its optical axis, and the rays reflected by the secondsurface of the modified Fresnel lens will use the upper part of thelens. Two smaller sizes of a modified Fresnel lens may also be used. Ineach case the solid object will not obscure its three-dimensional image.

As a result, a three-dimensional image is created and depth perceptionis observed with the unaided eye. While the conventional paraboloidreflecting mirror produces a highly directional image with a limitedfield of view accessible to few observers, the modified Fresnel lens incombination with a silvered second surface provides a vastly largerfield of view, is suitable for viewing by a mass audience and for thedirect projection of very large objects. When the fully modified Fresnellens replaces a regular aplanatic concave meniscus, equal magnificationis achieved for all three dimensions of a solid object as well as alarger field of view.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic optical ray diagram of the three-dimensionalimage projection system using the invention.

FIG. 2 shows an optical ray diagram of basic direct three-dimensionalprojection.

FIG. 2A shows a schematic of a lens with the shape of a thin wedge.

FIG. 3 shows a diagram of three aspherical surfaces which are elementsof the modified Fresnel lens system, the first two forming an asphericalmeniscus and the last being an aspherical mirror.

FIG. 4 shows an aplanatic concave meniscus, silvered at the back, whichforms the paraboloid mirror.

FIG. 5A shows the spherical front surface of the meniscus of FIG. 4,transformed into a modified Fresnel type lens.

FIG. 6 shows a schematic arrangement for projecting into space, twothree-dimensional images from a single object.

FIG. 7 is a schematic view which shows the projection of two images intospace from a single object using a Wollaston prism.

FIG. 8 is a schematic optical diagram which shows an arrangement forseparating laterally the images produced by the optical system of FIG.6.

FIG. 9 is a schematic optical diagram used in conjunction with thediagram of FIG. 8, to separate laterally the images produced by theoptical system of FIG. 6.

FIG. 10 is a schematic and geometric diagram for projectingthree-dimensional double images of a typical object such as a cube intospace.

FIG. 11 shows an optical schematic of a longitudinally split lensarrangement, with some dimensions increased for clarity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is provided a lens arrangement having aplano-spherical modified Fresnel lens at 10 having a silvered secondsurface 12. The light reflected from object 14 to lens 10 uses the lowerpart of the lens, i.e., below the optical axis 11. The rays reflected bythe second surface 12 pass through the modified Fresnel lens using theupper part of the lens (above the optical axis). A light source 16illuminates object 14 and beams of light emanating from it form aninverted image 18. Required longitudinal (depth) magnification isobtained by a fully modified Fresnel lens at 10. Viewing of thethree-dimensional image 18 by an audience preferably occurs from adirection generally towards lens 10, as is shown by arrow "D". Asplit-lens arrangement may also be used in the form of two smallermodified Fresnel lens.

FIG. 2 shows basic direct projection and how the modified Fresnel lens22 straightens the light rays by action of the silvered second surface24. Dispersion of light rays can be minimized by giving this lens theshape of a thin wedge 22a, per FIG. 2A. FIG. 2A shows a lens 22a in theform of a thin wedge-shape; such a thin wedge-shape serves to reducedispersion of light, and can be formed by two wedge-shaped prisms joinedat their bases or as a single unit. This lens can be advantageouslypositioned between other lenses to reduce the dispersion of light.

Thus, in FIG. 2 the object 20 is illuminated from a light source 21, forexample. Reflected rays such as a ray 23, for example, is incident on amodified Fresnel lens 22. After reflection from the modified Fresnellens 22, the ray 23 becomes incident on a further modified Fresnel lens24. After reflection from the element 24, the ray 23 is projected intospace, together with similar such rays, to form an enlargedthree-dimensional image 26 of the object in space.

For projecting large and very large objects, the three-dimensionaloptical systems should consist of a concave aspherical meniscus 28 and aconcave aspherical front mirror surface 30 located some distance behindthe meniscus, as shown by FIG. 3. The object 27 to be projected islocated in front of the meniscus 28. For optimum performance,characteristic shape of the optical surfaces, thickness of glass orplastic material, distance, size and focal length and number of Fresnelgrooves have to be found by trial and error. Actual forms and dimensionsdepend on the depth of the three-dimensional object.

The paraboloid mirror 32 in FIG. 4 is an aplanatic concave meniscuswhich is silvered on the back. Considering two points A and A' on itsoptical axis, each is the center of curvature of the first and secondsurfaces, respectively. The characteristic feature of this meniscus isthe ability to convert a wide-angle bundle of incident rays divergingfrom point A into a monocentric bundle. The rays, after having twicetravelled across the thickness of the glass (or plastic), pass throughpoint A', forming a diverging monocentric bundle, and are propagatedthrough a medium or space. The front surface 32a of this meniscus isspherical, the second or back surface 33 is paraboloid. The sphericalsurface 32a may be transformed into a modified Fresnel type lens 34 asshown in FIG. 5A by providing the segments of spherical surface 34 at34a, 34b, etc., and removing the unneeded curved portion of the lens asshown in dotted lines.

FIG. 6 shows another embodiment of the present invention, in which asingle object 40 is illuminated by light sources 16 and 38, and haslight rays directed from its surface through dual lenses 58 and 60 ontodual mirrors 42 and 44, which are conventional silvered-back surfacemirrors. After light rays 41 and 43 from the object surface arereflected by these mirrors 42 and 44, they again pass through lenses 58and 60 and produce separately projected rays 46 and 48 into space,whereby separate images 50 and 52 are obtained as magnified and invertedimages. In addition thereto, mirrors 54 and 56 may be placed in thepaths of rays 46 and 48, respectively, for use in conjunction with thearrangements of FIGS. 8 and 9 to be described. Adjacent to the mirrors42 and 44, modified Fresnel lenses 58 and 60 are provided. For example,these modified Fresnel lenses may have a focal length of 8 inches and beapproximately 11 inches square in dimensions. The object size may havemaximum dimensions of 4 inches, for example, and the distance betweenthe mirrors 42 and 44 and lenses 58 and 60, respectively, may beapproximately 2 inches. The planes of mirrors 42 and 44 may be inclinedfrom the vertical by about 25 degrees. Modified Fresnel lenses 58 and 60are preferably of the cycloid type. By moving mirrors 42 and 44 andvarying the spacing between the mirrors and each related lens 58 and 60,this controls the magnification of the final image.

FIG. 7 discloses another arrangement which is adapted for projectingrelatively small size objects, and for the purpose of producing doubleimages with the aid of a Wollaston prism. After object 62 is illuminatedby a light source 16, light rays 64 from the surface of the object aretransmitted by a modified Fresnel lens 66, which may be of theplano-convex, cycloid type. This lens may preferably have a diameter ofabout 3 inches and a focal length of about 4 inches. Spaced from themodified Fresnel lens 66 is a further modified Fresnel lens 68 which isalso of the plano-convex, cycloid type, having a diameter of about 3inches and a focal length of about 7 inches. The Wollaston prism 67 islocated between lenses 66 and 68 and is made of quartz or calcspar andis of the double refraction type with rectangular dimensions of 1 by 3inches. After being transmitted by the lens 68, rays 70 and 72, obtainedas a result of the separating function produced by the Wollaston prism,are projected into space to form double inverted and magnified images 74and 76, respectively.

FIG. 8 shows an optical arrangement whereby the images produced with thearrangement of FIG. 6 are separated laterally. For this purpose, lightrays 78 reflected by mirror 54 deflect the inverted image 82. Mirrors 54and 56 are preferably conventional silvered-back surfaces havingdimensions of 6 inches by 6 inches. A modified Fresnel lens 84 followingthe image 82 is preferably of the plano-convex, cycloid type having adiameter of 5.5 inches and a focal length of 24 inches. Lens 84comprises an erector lens whereby an erect image 86 is obtained afterthe rays transmitted by lens 84 are reflected further by a mirror 88,for example. A suitable position of lens 84 makes it possible to obtain,at will, positive or negative or unit magnifications. The separation ofthe double images amounts to a few yards. For more extended distances ofseparation of the images, a periscopic system is needed. Such a systemuses a series of three lenses, with unit magnification, to conduct thelight down a tube which is 8 inches in diameter and 40 feet long.

It is to be noted that a flat Fresnel lens and cycloid lens offerconsiderably larger fields of view, when compared to spherical lensesand mirrors. At the same time, two images of the same object serve todouble the field of view. In addition, the present invention providesthat the image can be produced almost of the same size as in aconventional two-dimensional movie screen. The effect is that the eyesof an observer are presented with a wide field of view as in normalvision. As a result, a mass audience may see the three-dimensionalimages at the same time.

FIG. 9 is similar to FIG. 8, in that rays 80, after reflection by mirror56 form the inverted image 90, which, after being transmitted by a lens92 similar to lens 84, is converted to an erect image 94, afterreflection by mirror 96. Mirror 96 corresponds to mirror 88.

FIG. 10 illustrates a projection arrangement in which the front-threefaces of a cube and the back-three faces of the same cube may beprojected into space. The object 98 is illuminated by light sources 16and 38 and after light rays 100 and 102 are reflected by mirrors 104 and106, the two images of the cube 108 and 110, respectively, are formed.Image 108 presents the back square faces of the cube, whereas image 110presents the front square faces of the cube. When using a cube measuring4 by 4 inches, for example, mirrors 104 and 106 are preferablyconventional, silvered-back surfaces, with dimensions 12 by 12 inchessquare. Lenses 112 and 114, which are spaced from the elements 104 and106, respectively, are preferably of the cycloid type, having a focallength of 8 inches and measuring 11 inches by 11 inches square.

When viewing a three-dimensional object such as a cube shown in FIG. 10,only three square faces out of six may be viewed simultaneously, whethersuch viewing is carried out with unaided eyes or with suitable opticalinstruments. The arrangement of FIG. 10 may also be used for visualinspections and defects of products produced by machines, for example.

FIG. 11 illustrates a projection arrangement using a longitudinallysplit lens. The lens is split into halves 118 and 120, and these arespaced from each other along the optical axis 122. After the surface ofthe object 116 is illuminated by a light source 16, the light rays 124are transmitted by the lens half 120 onto a reflector 126. Thisreflector then directs the light rays to lens half 118 from which thetransmitted light rays 128 form a magnified and inverted image 130. Thereflector 126 can be inclined from the vertical plane 132, and inclinedat the most suitable angle with respect to the optical axis. Also, thelens halves 118 and 120 can be separated transversely, axially andvertically as desired.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention,and therefore such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

I claim:
 1. A three-dimensional projection arrangement for projecting athree-dimensional image of an object into space for viewing by anaudience, said arrangement comprising: an object for which athree-dimensional image is projected; a light source oriented forilluminating said object; lens means comprising a multifocal refractinglens having multiple spherical zones on the side opposite from saidlight source, said lens being positioned to receive reflected light fromsaid object; andmirror means located behind said lens means away fromsaid light source, said mirror means being adjustable relative to thelens and adapted for receiving and reflecting an image of said objectfrom said lens means and reflecting said image back through said lensmeans, whereby said projection arrangement forms an enlargedthree-dimensional image projected in space for viewing by an audience,the magnification of said image being adjustable by moving said mirrormeans relative to the lens means.
 2. A three-dimensional imageprojection arrangement as defined in claim 1, wherein said lens meanscomprises a plano-spherical Fresnel lens and said mirror means comprisesa reflective surface located behind said Fresnel lens, light reflectedfrom said object being incident on a lower portion of said Fresnel lens,and light reflected from said reflective surface being reflected fromsubstantially the upper portion of said lens.
 3. A three-dimensionalimage projection arrangement as defined in claim 1, wherein said lensmeans comprises a split-lens unit.
 4. A three-dimensional imageprojection arrangement as defined in claim 1, wherein said lens is usedin combination with a substantially thin wedge shape positioned betweensaid other lens for reducing dispersion of light.
 5. A three-dimensionalimage projection arrangement as defined in claim 1, wherein said lensmeans comprises a concave aspherical meniscus and said mirror meanscomprises a concave aspherical front surface mirror behind saidmeniscus.
 6. A three-dimensional image projection arrangement as definedin claim 5, wherein said meniscus comprises an aplanatic concavemeniscus silvered on the rear and having two radii of curvature centeredat different locations along the optical axis.
 7. A three-dimensionalimage projection arrangement as defined in claim 6, wherein saidmeniscus converts a wide-angle bundle of incident rays diverging from apredetermined point on its optical axis into a monocentric bundle afterhaving twice travelled across the thickness of said meniscus.
 8. Athree-dimensional image projection arrangement as defined in claim 7,wherein said meniscus has a spherical front surface and a paraboloidsurface behind said spherical surface.
 9. A three-dimensional imageprojection arrangement as defined in claim 3, wherein said split lensunit comprises two halves spaced from each other along an optical axis,light rays from an object being transmitted by one lens half onto saidmirror means for directing said light rays to said other lens half toform a magnified and inverted image, said mirror means being inclinedrelative to the optical axis.
 10. A three-dimensional projectionarrangement for projecting three-dimensional images into space forviewing by a mass audience, comprising:(a) a dual light source forilluminating an object to be projected into space; (b) dual adjacentlens means each comprising a modified Fresnesl type lens have multiplefocal lengths; and (c) dual reflecting mirror means movably locatedbehind said dual lens means, whereby said lens means and said mirrormeans receive light rays from the illuminated object and form dualthree-dimensional images projected into space for viewing by saidaudience.
 11. A three-dimensional projection arrangement as defined inclaim 10, wherein light rays from said dual lens means and said dualmirror means are further reflected by second dual mirror means toprovide dual laterally separated three-dimensional images.
 12. Athree-dimensional projection arrangement as defined in claim 11, whereinthe laterally separated images are further projected by second dualmodified Fresnel lenses.
 13. A three-dimensional projection arrangementas defined in claim 1, wherein said lens is a modified Fresnel lenshaving a plurality of facets having multiple focal lengths.
 14. Athree-dimensional projection arrangement as defined in claim 1, whereinsaid lens has multiple curved surfaces in the shape of a cycloid.
 15. Athree-dimensional projection arrangement as defined in claim 1, whereinsaid lens provides substantially equal magnification of said image inall three dimensions.
 16. A three-dimensional projection arrangement asdefined in claim 1, wherein the three-dimensional image is viewedgenerally towards said lens means.
 17. A three-dimensional projectionarrangement for projecting a three-dimensional image of an object intospace for viewing by an audience, said arrangement comprising:(a) anobject for which the three-dimensional image is projected; (b) a lightsource for illuminating said object; (c) a modified Fresnel lens havingspherical zones in the form of strips and a plurality of facets havingmultiple focal lengths, said facets being located on the side oppositefrom said light source; and (d) mirror means located behind said lensmeans away from said light souce, said mirror means being adjustablerelative to the lens and adapted for receiving and reflecting an imageof said object from said lens back through said lens, whereby saidprojection arrangement forms an enlarged three-dimensional imageprojected into space for viewing by an audience in the general directionof said lens, the magnification of said image being adjustable by movingsaid mirror means relative to the lens.